This invention relates generally to the field of optical communications, and in particular, to a method and apparatus for providing all-optical wavelength conversion and/or 2R regeneration (reamplification and/or reshaping) with wavelength filters.
All-optical wavelength converters are increasingly important as alternatives to optical-to-electrical- to-optical wavelength converters in wavelength division multiplexing (WDM) optical communications systems. Such converters are needed to switch from one wavelength to another or also to regenerate a degraded signal.
All-optical wavelength converters exploit the effect of an input-signal in a nonlinear medium to transfer the input-signal information by means of the nonlinear medium onto a continuous wave (cw) signal. The cw signal (which might be at a new wavelength) then carries the information of the input-signal, and the input-signal itself is not used anymore. Since both the cw and the input-signal were guided into the same nonlinear medium, they have to be separated after wavelength conversion. While this separation can be done with an external wavelength filter, external wavelength filters add to the cost of a product. In addition, there are cases where the incoming wavelength and the converted wavelength have the same wavelength (e.g. if the device is used as a regenerator). In this case, an external wavelength filter can not separate the incoming and converted wavelength, and the device can not be used. In addition, external wavelength filters restrict the application range to cases where the wavelength of the converted signal does not change, since an external wavelength filter is usually tuned only to a single wavelength.
A delayed interference all-optical wavelength converter is arranged and operated to convert a pulsed input signal Pin at xcex1 into the wavelength converted signal Pconv at xcex2, where xcex1 and xcex2 are different. A delayed interference all-optical wavelength regenerator is similar, but is arranged and operated to reshape a pulsed input signal Pin into the wavelength converted signal Pconv, where the wavelengths of the input signal and the converted signal may be different or the same. It is to be understood here that the arrangement of the present invention can be a wavelength converter and a wavelength regenerator at the same time, and that the functions performed by a regenerator or converter can include aspects or capabilities of the other. The converter/regenerator comprises an input-signal coupling unit for receiving the pulsed input signal and supplying it to one input of a modulation section, the other input to which is a carrier signal Pcw. The output of the modulation section Pint, which is generally speaking, a phase modulated signal which may also have an amplitude modulated component, is applied to a delay interference section that is arranged to transform Pint into a primarily amplitude modulated signal. In accordance with the invention, a wavelength filtering element or arrangement that can enable partial or even complete input-signal wavelength filtering, is either a part of the modulation section, the coupling unit, the delay-interference section or an integral part of the whole configuration.